Creatinine: normal range, eGFR, and what abnormal results mean
Among all the tests a doctor orders during a routine check-up or after complaints of fatigue and swelling, creatinine occupies a special place. Abnormal levels rarely produce clear symptoms on their own — and that’s exactly the risk. Chronic kidney disease (CKD) is largely silent in its early stages: people feel reasonably well while their kidneys are already operating at only 60–70% of capacity.
Creatinine is the end product of creatine phosphate breakdown in muscle tissue. It is produced at a relatively stable rate and is continuously filtered out of the blood by the kidneys and excreted in urine. When the kidneys begin to filter less efficiently, creatinine accumulates in the blood — and that’s what the test captures.
There is an important nuance, though: the raw creatinine number tells you relatively little about true kidney function. The real clinical value begins when it is converted into estimated glomerular filtration rate (eGFR) — a figure that accounts for age and sex and gives a far more accurate picture of how the kidneys are performing.
What creatinine is
Creatine phosphate stores energy inside muscle cells. During muscle activity it breaks down to creatine, which is further metabolised to creatinine. This metabolic by-product enters the bloodstream and is cleared by the kidneys within hours.
An important characteristic: the rate at which creatinine is produced depends directly on muscle mass. That is why the normal range is higher for men than women, and somewhat lower in older adults due to natural age-related muscle loss. It also means that in a highly athletic individual, a result that sits above the standard reference range may be entirely normal for that person.
Not to be confused with the sports supplement. Creatine (creatine monohydrate) and creatinine are different substances. Creatine is a supplement used to improve athletic performance; in the body it is converted to creatinine. Taking creatine at typical doses of 3–5 g per day can moderately raise serum and urinary creatinine, which matters when interpreting your results.
The test uses venous blood. Results are reported as µmol/L (standard in most European and Ukrainian laboratories) or as mg/dL (common in US and international references). The conversion factor is: 1 mg/dL ≈ 88.4 µmol/L.
Normal creatinine range
Reference values differ considerably by sex and age. The ranges below reflect values used by most clinical guidelines — your laboratory may report slightly different limits depending on its measurement method.
| Group | µmol/L | mg/dL |
|---|---|---|
| Men (≥19 years) | 62–115 | 0.70–1.30 |
| Women (≥19 years) | 53–97 | 0.60–1.10 |
| Children 1–13 years | 27–62 | 0.30–0.70 |
| Adolescents 14–18 years | 53–115 | 0.60–1.30 |
| Pregnant | 25–40% below non-pregnant range | — |
Pregnancy: During pregnancy the kidneys increase filtration volume through physiological hyperfiltration, so creatinine naturally falls and may sit below the standard lower reference limit. This is not pathological.
A key reminder: don’t apply the table directly if you have an unusual body composition — very low or very high muscle mass. In those situations, the eGFR calculation provides a far more accurate assessment of kidney function than the raw creatinine number alone.
eGFR — the main kidney function metric
The glomerular filtration rate (GFR) — or estimated GFR (eGFR) — tells you how many millilitres of blood plasma the kidneys cleanse per minute. For a healthy young adult, a normal value is approximately 90–120 mL/min/1.73 m². After the age of 40, eGFR physiologically declines by roughly 1 mL/min per year.
In 2021 the calculation standard was updated: the CKD-EPI 2021 equation (Inker et al., NEJM) replaced the 2009 version and removed the race-based adjustment, improving accuracy and equity of assessment across all patients. This equation is now recommended by most international nephrology organisations.
Laboratories typically calculate eGFR automatically alongside the serum creatinine result and include it on the report. If it isn’t included, your doctor can calculate it directly or use an online calculator.
CKD stages by eGFR
| Stage | eGFR (mL/min/1.73 m²) | Description |
|---|---|---|
| G1 | ≥90 | Normal or high function |
| G2 | 60–89 | Mildly decreased |
| G3a | 45–59 | Mildly to moderately decreased |
| G3b | 30–44 | Moderately to severely decreased |
| G4 | 15–29 | Severely decreased |
| G5 | <15 | Kidney failure (end stage) |
An important detail: a CKD stage is determined not by eGFR alone, but also by the level of protein (albumin) in the urine. An eGFR of 65 with a normal urinalysis and an eGFR of 65 with significant proteinuria are clinically quite different situations. That’s why a doctor evaluates both markers together.
It’s also worth knowing: a single low eGFR result is not sufficient for a CKD diagnosis. The diagnosis requires confirmation on at least two occasions at least three months apart.
Elevated creatinine — what it means
A raised creatinine always warrants careful evaluation. The causes range from trivial (mild dehydration before the test) to serious (acute or chronic kidney injury).
Acute cause: dehydration and physical load
The most common reason for an isolated moderate elevation with no prior history is functional: the kidneys filter less when blood volume is low. This happens with:
- Dehydration (inadequate fluid intake, hot weather, vomiting, diarrhoea);
- Intensive exercise in the 24 hours before the test (muscle breakdown temporarily increases creatinine production);
- A large amount of red meat the evening before (muscle proteins from food add to the creatinine load).
In these situations, repeating the test 3–5 days later under normal preparation conditions typically returns the result to normal.
Acute kidney injury (AKI)
A sudden sharp rise in creatinine — particularly in hospitalised patients or following surgery — may indicate acute kidney injury. Common causes include shock, severe infection (sepsis), cardiac or vascular surgery, contrast-induced nephropathy (from CT contrast agents), and certain medications — particularly aminoglycoside antibiotics (gentamicin), non-steroidal anti-inflammatories (ibuprofen, diclofenac), and ACE inhibitors or ARBs in a setting of significant dehydration.
Chronic kidney disease (CKD)
A gradual, sustained rise in creatinine over months and years is the most common pattern seen in outpatient practice. The main underlying causes of CKD are:
- Diabetic nephropathy — the leading cause of CKD worldwide. Prolonged hyperglycaemia damages the microvasculature of the renal glomeruli.
- Hypertensive nephropathy — chronically elevated blood pressure causes ischaemia and fibrosis of kidney tissue over time.
- Glomerulonephritis — inflammatory damage to the glomeruli from various immune-mediated causes.
- Urinary tract obstruction — stones, an enlarged prostate, or tumours create back-pressure on the kidneys.
When persistently elevated creatinine or an eGFR below 60 is detected, additional investigations are ordered: urinalysis for proteinuria, renal ultrasound, and where appropriate, more specific markers. As eGFR declines, secondary hyperparathyroidism and disrupted mineral-bone metabolism are common, so monitoring of calcium and PTH becomes a routine part of CKD management at the later stages.
Low creatinine
A below-normal creatinine is less common but also worth understanding.
Significant muscle atrophy is the most common cause: prolonged immobilisation (bed rest after injury or surgery), neurological conditions (myopathies, muscular dystrophy), or extreme wasting associated with cancer or critical illness.
Pregnancy is a physiological cause — eGFR rises and creatinine falls. This is normal and expected.
Long-term plant-based diet — vegans and vegetarians tend to have somewhat lower baseline creatinine levels because their diet contains fewer animal-source muscle proteins.
Severe liver disease — the liver synthesises creatine, which is the precursor to creatinine. In cirrhosis or acute liver failure, creatine synthesis falls and creatinine may be correspondingly low.
An isolated low creatinine without symptoms generally does not require treatment, but the underlying cause may warrant investigation if the reduction is marked or persistent.
How to prepare for the test
Unlike fasting glucose, strict fasting is not required for a creatinine test taken in isolation. However, if the test is ordered as part of a broader panel that includes glucose or a lipid profile, follow the preparation instructions for the full panel.
Practical recommendations:
- Avoid intense exercise in the 24 hours before the test. Strength training and long runs temporarily raise creatinine through increased muscle breakdown.
- Don’t eat a large amount of red meat the night before. A steak or large portion of meat at dinner before the test can produce a moderate rise in your result.
- Hydration — keep it normal. Drink water as you usually would. Don’t deliberately “pre-load” with fluid before the test — that will produce a falsely low result.
- Time of day is not critical. You can have blood drawn in the morning or during the day.
If you’re having a panel that includes a complete blood count (CBC), follow the CBC preparation guidance — typically an early-morning draw, either fasting or after a light meal.
How HealthLab helps you track kidney function
A single creatinine result is only a snapshot. Kidney function changes slowly, and the clinical value of the marker increases substantially when you have a trend: is the level rising year on year, staying stable, or recovering after treatment? In patients with diabetes or hypertension, creatinine and eGFR are monitored regularly — and comparing results over time is an integral part of their care.
If you struggle with unexplained fatigue, creatinine is one of the markers in the standard screening panel, and tracking it alongside others gives you the most complete picture of what’s happening.
HealthLab automatically recognises creatinine and other biomarkers from PDF lab reports issued by any laboratory and builds a trend chart over time. You can see how the marker moves from test to test — no manual data entry, no spreadsheets.
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Frequently Asked Questions
Do I need to fast before a creatinine test?
Strict fasting is not required for an isolated creatinine test. That said, avoid a large serving of red meat the night before and skip intense exercise in the 24 hours beforehand. If the test is part of a combined panel that includes glucose or a lipid profile, follow the preparation instructions for the whole panel — usually an early-morning draw either fasting or after a light meal.
What does an eGFR of 65 mean? Do I have CKD?
An eGFR of 65 falls into stage G2 — “mildly decreased” kidney function. On its own it is not a diagnosis of CKD: diagnosis requires either a persistently low eGFR or evidence of kidney damage (such as protein in the urine) confirmed on at least two separate occasions at least three months apart. If your urinalysis is normal and you have no symptoms, your doctor will most likely schedule a repeat test in a few months. Do not draw conclusions or make changes on your own — this is a conversation to have with your doctor.
How often should I test if my eGFR is normal?
For healthy adults without risk factors, checking creatinine once every one to two years as part of a general check-up is sufficient — for example as part of a complete blood count or biochemistry panel. If you have risk factors — type 2 diabetes, hypertension, obesity, or a family history of kidney disease — your doctor will typically recommend more frequent monitoring, usually every 6–12 months.
Does creatine supplementation affect my creatinine result?
Yes. Creatine monohydrate is converted to creatinine in the body. Taking standard doses (3–5 g per day) can raise serum and urinary creatinine, potentially pushing the result above the upper reference limit. Let your doctor know if you take this supplement so they can account for it when interpreting your result. They will typically either suggest pausing supplementation for a few weeks before a planned test, or assess eGFR in the context of your muscle mass.
This material does not replace clinical advice. Interpreting laboratory results always requires clinical context.
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